With its showroom debut expected to fall around the middle of 2011, a heavily camouflaged prototype of the 2012 Mercedes-Benz ML-Class has been spied testing alongside its counterparts in the luxury SUV market this week.

Based on our spy photos and drawing on the styling of Mercedes' newer models, our speculative rendering (see gallery) also offers a glimpse at what might lurk beneath the test car’s heavy camouflage.

While the wheelbase appears more or less unchanged from the current model, shorter overhangs front and back point to a slightly more compact body than the 2009 ML-Class.

The camouflage obscures virtually all of the next-generation ML's finer details, although it's clear that the prototype shares a roof and beltline similar to that of the 2009 model.

Reports out of Europe suggest that the new ML-Class will include a diesel-electric hybrid in its line-up, while a petrol-electric hybrid Mercedes is expected to land before the end of 2011.

To keep development and production costs down, the 2012 ML-Class is likely to share many of its components and underpinnings with R-Class and G-Class models.

To help it achieve a greener image and meet strict European standards, the new ML is expected to offer a 2.2 litre four-cylinder diesel engine developing 152kW, while a 168kW V6 diesel and a 248kW petrol V6 will likely round out the engine options.

For performance buyers, the AMG model should feature direct-injection and forced induction by way of a pair of turbochargers, delivering upwards of 425kW.